The undo button causes the table control to go inactive

Hello,

we upgarded to Confluence Version 5.8.5 a few days ago and just now discovered the following bug:

When you hit the "undo" Button (or use ctrl+z) the controlls for tables goes inactive.

See atteched Screenshots:
Before: Before I hit the undo Button
After: After I hit the undo Button.

At the moment I have to save (or discared the changes) and then change back into the edit mode in order to get the table controls active again.